In this sort of apparatus, a thermocouple is provided as a thermal sensor to detect the combustive condition on a burner plate. In this instance, the thermocouple generates an output, the magnitude of which corresponds to air-fuel ratio at a certain quantity of combustion.
Therefore, the output range from the thermocouple when appropriate air-fuel ratio is obtained is previously determined at a certain quantity of combustion. In so doing, the apparatus decides the combustion to be in abnormal condition so as to interrupt it when the thermocouple generates the output exceeding to or short of the output range.
The above output range, however, displaces in response to the quantity of combustion which is liable to change during operation.
As a consequence, there is a possibility that the apparatus interrupts the combustion depending upon its quantity even though the air-fuel ratio falls within an appropriate range.
2. Summary of the Invention
It is an object of the present invention to provide a burner apparatus which is capable of positively stopping combustion on a burner plate regardless of the quantity of the combustion when air-fuel ratio deviates from within a certain appropriate range.
According to the present invention, there is provided a burner plate on which fuel gas is ignited, a thermal sensor which generates an output voltage in response to the combustion of the fuel gas so as to detect an air component of the fuel gas, means for causing the output from the thermal sensor to correspond to the quantity of combustion on the burner plate, and a safety circuit which stops the combustion on the burner plate when the output of the thermal sensor displaces from a magnitude within a certain range. With this structure, a burner apparatus is able to positively stop combustion on a burner plate regardless of the quantity of the combustion when the air-fuel ratio deviates from a predetermined magnitude.